Photoconductive elements containing ionic cycloheptenyl photoconductive compounds



US. Cl. 96-15 10 Claims ABSTRACT OF THE DISCLOSURE Photoconductive elements containing certain substituted cycloheptenyl compounds as photoconductors are' described. The described photoconductors can be sensitized and charged either negatively or positively.

This application is a continuation-in-part of US. Ser. No'. 425,051, filed Ian. 12, 1965, now abandoned.

This invention relates to electrophotography, and in particular to photoconductive compositions and elements.

The process of xerography, as disclosed by Carlson in US. 2,297,691, employs an electrophotographic element comprising a support material bearing a coating of a normally insulating material whose electrical resistance varies with the amount of incident actinic radiation it receives during an imagewise exposure. The element, commonly termed a photoconductive element, is first fiiven a uniform surface charge, generally in the dark after a suitable period of dark adaptation. It is then exposed to a pattern of actinic radiation which has the effect of differentially reducing the potential of the surface charge in accordance with the relative energy contained in various parts of the radiation pattern. The differential surface charge or electrostatic latent image remaining on the electrophotographic element is then made visible by contacting the surface with a suitable electroscopic marking material. Such marking material or toner, whether contained in an insulating liquid or on a dry carrier, can be deposited on the exposed surface in accordance with either the charge pattern or in the absence of charge pattern as desired. The deposited marking material can then be either permanently fixed to the surface of the sensitive element by known means such as heat, pressure, solvent vapor, or the like, or transferred to a second element to which it can similarly be fixed. Likewise, the electrostatic latent image can be transferred to a second element and developed there.

Various photoconductive insulating materials have been employed in the manufacture of electrophotographic elements. For example, vapors of selenium and vapors of selenium alloys deposited on a suitable support and particles of photoconductive zinc oxide held in a resinous, film-forming binder have found wide application in present-day document copying applications.

Since the introduction of electrophotography, a great many organic compounds have also been screened for their photoconductive properties. As a result, a very large number of organic compounds are known to possess some degree of photoconductivity. Many organic compounds have revealed a useful level of photoconduction and have been incorporated into photoconductive compositions. Optically clear organic photoconductor-containing elements having desirable electrophotographic properties can be especially useful in electrophotography. Such electrophotographic elements can be exposed through a transparent base if desired, thereby providing unusual flexi- United States Patent 3,533,786 Patented Oct. 13, 1970 "ice bility in equipment design. Such compositions, when coated as a film or layer on a suitable support also yield an element which is reusable; that is, it can be used to form subsequent images after residual toner from prior images has been removed by transfer and/or cleaning. Thus far, the selection of organic compounds for incorporation into photoconductive compositions to form electrophotographic layers has proceeded on a compoundby-compound basis. Nothing has yet been discovered from the large number of different photoconductive substances tested which permits effective prediction and therefore selection of partiuclar compounds exhibiting the desired electrophotographic properties.

It is, therefore, an object of this invention to provide a novel class of organic photoconductors having enhanced photosensitivity when electrically charged.

It is another object to provid novel photoconductoroontaining compositions which exhibit high electrical speeds.

It is also an object to provide novel photoconductorcontaining compositions which can be positively and negatively charged.

It is another object to provide novel transparent electrophotographic elements having high speed characteristics.

It is a further object of this invention to provide novel electrophotographic elements useful for producing images electrophotographically by reflex or birefiex processes.

These and other objects of this invention are accomplished with electrophotographic elements having coated thereon organic photoconductive compositions containing non-ionic cycloheptenyl compounds as photoconductors.

The cycloheptenyl compounds can be substituted, if desired, in the nucleus with a wide variety of substituents such as (a) an aryl radical including substituted as well as unsubstituted aryl radicals, (b) a hydroxy radical, (c) an azido radical, (d) a heterocyclic radical having 5 to 6 atoms in the heterocyclic nucleus and at least one hetero nitrogen atom, and including substituted and unsubstituted hererocyclic radicals, and (e) an oxygen linked cycloheptenyl moiety. The substitution on the cycloheptenyl nucleus occurs on an unsaturated carbon atom (i.e., a carbon atom having at least a double bond) when the cycloheptenyl moiety is a conjugated triene with no aromatic structure fused thereto. However, if there is at least one aromatic structure fused to the cycloheptenyl moiety, then the substituents are attached to a saturated carbon atom (i.e., a carbon atom with no double bonds).

The preferred photoconductors of this invention are represented by the following structures:

where E and G can be either:

(a) a phenyl radical, (b) a naphthyl radical, (c) a heterocyclic radical having 5 to 6 atoms in the heterocyclic nucleus and at least one hetero nitrogen atom,

D can be any of the substituents defined for E and G above and is attached to a carbon atom in the cycloheptenyl nucleus having adouble bond; (R and R (R 3 and R (R and R and (R and R are together the necessary atoms to complete a benzene ring fused to the cycloheptenyl nucleus.

Some typical photoconductors of this invention are:

2 (10) 4 5-( 5H-dibenzo[a,d] cycloheptenyl) ]-1-dimethylaminonaphthalene;

(11) N,N-diethyl-3-methyl-4-[5-(10,11-dihydro-5H- dibenzo- [a,d] cycloheptenyl) aniline;

(12) 3- 4-dimethylaminophenyl 1 ,3 ,5 -cycloheptatriene (l3) 3- (4-diethylamino-2-methylphenyl) -1,3,5-cycloheptatriene;

(14) 3-(4-dirnethylaminonaphthyl) -1,3,5-cyclohepta triene; and

( 15) N,N-diethyl-3-methyl-4- [5 5 H-dibenzo [a,d] cycloheptenyl) aniline.

Electrophotographic elements of the invention can be prepared with the photoconducting compounds of the invention in the usual manner, i.e., by blending a dispersion or solution of a photoconductive compound together with a binder, when necessary or desirable, and coating or forming a self-supporting layer with the photoconductor-containing material. Mixtures of the photoconductors described herein can be employed. Likewise, other photoconductors known in the art can be combined with the present photoconductors. In addition, supplemental materials useful for changing the spectral sensitivity or electrophotosensitivity of the element can be added to the composition of the element when it is desirable to produce the characteristic effect of such materials.

Sensitizing compounds useful with the photoconductive compounds of the present invention can include a wide variety of substances such as pyrylium, thiapyrylium, and selenapyrylium salts of US. Pat. 3,250,615, issued May 10, 1966; fluorenes, such as 7,12-dioxo-13- dibenzo(a,h)fluorene, 5,10-dioxo 4a,11 diazabenzo(b) fluorene, 3,13-dioxo-7-oxadibenzo(b,g)fluorene, trinitrofluorenone, tetranitrofluorenone and the like; aromatic nitro compounds of US. Pat. 2,610,120; anthrones of US. Pat. 2,670,285; quinones of US. Pat. 2,670,286; benzophenones of US. Pat. 2,670,287; thiazoles of US. Pat. 2,732,301; mineral acids; carboxylic acids, such as maleic acid, dichloroacetic acid, and salicylic acid; sulfonic and phosphoric acids; and various dyes such as triphenylmethane, diarylmethane, thiazine, azine, oxazine, Xanthene, phthaliene, acridine, azo anthraquinone dyes and many other suitable sensitizing dyes. The preferred sen sitizers for use with the compounds of this invention are pyrylium and thiapyrylium salts fluorenes, carboxylic acids, and triphenylmethane dyes.

Where a sensitizing compound is to be used within a photoconductive layer as disclosed herein it is conventional practice to mix a suitable amount of the sensitizing compounds with the coating composition so that, after thorough mixing, the sensitizing compound is uniformly distributed throughout the desired layer of the coated element. In preparing the photoconducting layers, no sensitizing compound is needed for the layer to exhibit photoconductivity. The lower limit of sensitizer required in a particular photoconductive layer is, therefore, zero. However, since relatively minor amounts of sensitizing compound give substantial improvement in the electrophotographic speed of such layers, the use of some sensitizer is preferred. The amount of sensitizer that can be added to a photoconductor-incorporating layer to give effective increases in speed can vary Widely. The optimum concentration in any given case will vary with the specific photoconductor and sensitizing compound used. In general, substantial speed gains can be obtained where an appropriate sensitizer is added in a concentration range from about 0.0001 to about 30 percent by weight based on the weight of the film-forming coating composition. Normally, a sensitizer is added to the coating composition in an amount by weight from about 0.005 to about 5.0 percent by weight of the total coating composition.

Preferred binders for use in preparing the present photoconductive layers are film-forming polymeric binders having fairly high dielectric strength which are good electrically insulating film-forming vehicles. Mater als of this type comprise styrene-butadiene copolymers; silicone resins; styrene-alkyd resins; silicone-alkyl resins; soyaalkyl resins; poly(vinyl chloride); poly(vinylidene chloride; vinylidene chloride-acrylonitrile copolymers; poly- (vinyl acetate); vinyl acetate-vinyl chloride copolymers; p'oly(vinyl acetals), such as poly(vinyl butyral); polyacrylic and methacrylic ester, such as poly(methylmethacrylate), poly(n-butylmethacrylate), poly(isobutyl meth acrylate), etc.; polystyrene; nitrated polystyrene; polymethylstyrene; isobutylene polymers; polyesters such as poly(ethylenealkaryloxyalkylene terephthalate); phenolformaldehyde resins; ketone resins; polyamide; polycarb'onates; polythiocarbonates; poly(ethyleneglycolo-bishydroxyethoxyphenyl propane terephthalate); etc. Methods of making resins of this type have been described in the prior art, for example, styrene-alkyd resins can be prepared according to the method described in U.S. Pats. 2,361,019 and 2,258,423. Suitable resins of the type contemplated for use in the photoconductive layers of the invention are sold under such tradenames as Vital PE-101, Cyrnac, Piccopale 100, Saran 1 -220 and Lexan 105. Other types of binders which can be used in the photoconductive layers of the invention include such materials as paraffin mineral Waxes, etc.

Solvents of choice for preparing coating compositions of the present invention can include a number of solvents such as benzene, toluene, acetone, Z-butanone, chlorinated hydrocarbons, e.g., methylene chloride, ethylene chloride, etc., ethers, e.g., tetrahydrofuran, or mixtures of these solvents, etc.

In preparing the coating composition useful results are obtained where the photoconductor substance is present in an amount equal to at least about 1 weight percent of the coating composition. The upper limit in the amount of photoconductor substance present can be widely varied in accordance with usual practice. In those cases where a binder is employed, it is normally required that the photoconductor substance be present in an amount from about 1 weight percent of the coating composition to about 99 weight percent of the coating composition. A preferred weight range for the photoconductor substance in the coating composition is from about 10 weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support can vary widely. Normally, a coating in the range of about 0.001 inch to about 0.01 inch before drying is useful for the practice of this invention. The preferred range of coating thickness was found to be in the range from about 0.002 inch to about 0.006 inch before drying although useful results can be obtained outside of this range.

Suitable supporting materials for coating the photoconductive layers of the present invention can include any of a wide variety of electrically conducting supports, for example, paper (at a relative humidity above 20 percent); aluminum-paper laminates; metal foils such as aluminum foil, zinc foil, etc.; metal plates, such as aluminum, copper, zinc, brass, and galvanized plates; vapor deposited metal layers such as silver or aluminum and the like. An especially useful conducting support can be prepared by coating a support material such as polyethylene terephthalate with a layer containing a semiconductor dispersed in a resin. Such conducting layers both with and without insulating barrier layers are described in US. Pat. 3,245,833. Likewise, a suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of maleic anhydride and a vinyl acetate polymer. Such kinds of conducting layers and methods for their optimum preparation and use are disclosed in US. Pats. 3,007,901 and 3,267,807.

The elements of the present invention can be employed in any of the well-known electrophotographic processes which require photoconductive layers. One such process is the aforementioned xerographic process. As previously explained, in a process of this type the electrophotographic element is given a blanket electrostatic charge by placing the same under a corona discharge which serves to give a uniform charge to the surface of the photoconductive layer. This charge is retained by the layer owing to the substantial insulating property of the layer, i.e., the low conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photoconducting layer is then selectively dissipated from the surface of the layer by exposure to light through an image-bearing trans parency by a conventional exposure operation such as, for example, by contact-printing technique, or by lens projection of an image, etc., to form a latent image in the photoconducting layer. By exp'osure of the surface in this manner, a charged pattern is created by virtue of the fact that light causes the charge to be conducted away in proportion to the intensity of the illumination in a particular area. The charge pattern remaining after exposure is then developed, i.e., rendered visible, by treatment with a medium comprising electrostatically attractable particles having optical density. The developing electrostatically attractable particles can be in the form of a dust, e.g., powder, pigment in a resinous carrier, i.e., toner, or a liquid developer may be used in which the developing particles are carried in an electrically insulating liquid carrier. Methods of development of this type are widely known and have been described in the patent literature in such patents, for example, as US. Pat. 2,297,691 and in Australian Pat. 212,315. In processes of electrophotographic reproduction such as in xerography by selecting a developing particle which has as one of its components, a low-melting resin, it is possible to treat the developed photoconductive material with heat and cause the powder to adhere permanently to the surface of the photoconductive layer. In other cases, a transfer of the image formed on the photoconductive layer can be made to a second support, which would then become the final print. Techniques of the type indicated are well known in the art and have been described in a number of U.S. and foreign patents, such as US. Pats. 2,297,691 and 2,551,582, and in RCA Review, vol. 15 (1954), pages 469-484.

The present invention is not limited to any particular mode of use of the new electrophotographic materials, and the exposure technique, the charging method, the transfer (if any), the developing method, and the fixing method as Well as the materials used in these methods can be selected and adapted to the requirements of any particular technique.

Electrophotographic materials according to the present invention can be applied to reproduction techniques wherein different kinds of radiations, i.e., electromagnetic radiations as well as nuclear radiations, can be used. For this reason, it is pointed out herein that although materials according to the invention are mainly intended for use in connection with methods comprising an exposure,

the term electrophotography wherever appearing in the description and the claims, is to be interpreted broadly and understood to comprise both xerography and xeroradiography.

The invention is further illustrated by the following examples which include preferred embodiments thereof.

EXAMPLE 1 Preparation of bis-[5-(5H-dibenzo[a,d] cycloheptenyl)] ether and S-hydroxy-SH-dibenzo [a,d]cycloheptene These compounds are prepared according to the procedure of G. Berti, Gazz. Chim, Ital, 87, 293 (1957).

EXAMPLE 2 Preparation of 5-azido-5H-dibenzo[a,d] cycloheptene Preparation of 1-[5-(5H-dibenzo[a,d]cycloheptenyl) 4,5 -dicarbomethoxy- 1 ,2,3-triazole A mixture of 1.0 g. (0.004 mole) of 5-azido-5H-dibenzo[a,d]cycloheptene, 1.0 g. (0.007 mole) of dimethyl acetylenedicarboxylate and 10 ml. of carbon tetrachloride is heated at reflux for one hour, concentrated, and the residue recrystallized from ethyl alcohol giving 1.2 g. of product (75 percent). The material melts at 162 C., resolidifies and melts again at 204-206" C.

EXAMPLE 4 Preparation of 1- [5- SH-dibenzo [a,d] cycloheptenyl) 4,5-dibenzoyl-1,2,3-triazole The procedure of Example 3 is used with. the exception that an equivalent amount of dibenzoylacetylene is used in place of the dimethyl acetylenedicarboxylate. The product, obtained in 29 percent yield, has a melting point of 163 C. After resolidifying, the melting point is 189- 190 C.

EXAMPLE 5 Preparation of 1-{5-(10,11-dihydro 5H-dibenzo[a,d]cycloheptenyl)}-4,5-dicarbomethoxy 1,2,3-triazole and l-{5-( 10,11-dihydro 5H-dibenzo[a,d] cycloheptenyl 4,5-dibenzoyl-1,2,3-triazole These compounds are prepared by the methods of Examples 3 and 4, respectively, using as starting materials the analogous 11,12-dihydro substituted compounds.

EXAMPLE 6 Preparation of 4- [S-(SH-dibenzo [a,d]cycloheptenyl) N,N-dimethyl aniline One gram of 5-chloro 5H-dibenzo[a,d]cycloheptene and 2 grams of N,N-dimethyl aniline are heated at reflux in 30 ml. of benzene for 30 minutes. The solvent is removed and the residue washed with dilute sodium hydroxide solution before extraction into methylene chloride. Removal of the solvent leaves an oil which crystallizes upon the addition of ethanol. The product is obtained in 66 percent yield, has a melting point of 141- 142 C. and the following elemental analysis:

Calculated for C H N (percent): C, 88.6; H, 6.8; N, 4.5. Found (percent): C, 88.4; H, 6.7; N, 4.5.

EXAMPLE 7 Preparation of ,N,N diethyl-3-methyl-4-[S-(SH-dibenzo- [a,d]cycloheptenyl)laniline and 4-[5 (5H dibenzo- [a,d] cycloheptenyl) ]-1-dimethylamino naphthalene These compounds are prepared by the method of Example 6 using N,N-diethyl 3-methyl aniline and 1-dimethylamino naphthalene, respectively, in the alkylation reaction in place of N,N-din1ethyl aniline.

EXAMPLE 8 Preparation of N,N-diethyl-3-methyl-4-[5-( 10,11-r1ihydro- SH-dibenzo [a,d] cycloheptenyl) aniline One gram of 5-chloro-l0,l1-dihydro 5H-dibenzo[a,d] cycloheptene and 2 grams of N,N-diethyl-3-methyl aniline are heated at reflux in ml. of benzene for 30 minutes. The solvent is removed and the residue is washed with dilute sodium hydroxide solution before extraction with methylene chloride. After the solvent is removed, the resultant oil crystallizes upon the addition of ethanol.

EXAMPLE 9 Preparation of 3-(4-dimethylaminophenyl)- 1,3,5 -cycloheptatriene A solution of 9.0 g. (0.050 mole) of tropylium tetrafluoroborate in 70 ml. of acetonitrile is added dropwise to a stirred solution of 18 g. (0.15 mole) of N,N-dimethylaniline in ml. acetonitrile. After the mixture has been stirred overnight at room temperature, the solvent is removed and the residue is treated with excess. dilute base. The mixture is extracted with ether and the ether solution is subsequently washed with Water and dried. Removal of the solvent and any excess N,N-dimethylaniline is followed by distillation of the residue. 8.4 grams (80 percent) of yellow oil, B.P. l36-l38 C./0.15 mm. remains. The oil solidifies on standing and melts at 3848 C. Several recrystallizations of this material from methanol give 1.5 g. of 3-(4-din1ethylaminophenyl) 1,3,5-cycloheptatriene, M.P. 6465 C.

Analysis.-Calcd. for C H N (percent): C, 85.3; H, 8.1; N, 6.6. Found (percent): C, 85.5; H, 7.7; N, 6.4.

EXAMPLE 10 Preparation of 3-(4-diethylamino-2-methylphenyl) cycloheptatriene Alkylation of N,N-diethyl-m-toluidine with tropylium tetrafluoroborate is carried out substantially by the procedure described in Example 9 to produce an 83 percent yield of product boiling at 1346 C./ 0.08 mm.

EXAMPLE 11 Preparation of 3-(4-dimethylaminonaphthyl)-1,3,5-cycloheptatriene A solution of 18 g. (0.10 mole) of tropylium tetrafluoroborate in 200 ml. of acetonitrile is added dropwise to a solution of 34 g. (0.20 mole) of l-dimethylaminonaphthalene in 100 ml. of acetonitrile. After the mixture stands overnight, the solvent is removed and the residue is treated with excess dilute sodium hydroxide. The organic material is taken up in methylene chloride, washed with water, dried and diluted to give 21.7 g. (83 percent) of oil, B.P. 144-452 C./0.06 mm. The N.M.R. spectrum of this material shows a doublet at 7.297 and a triplet at 7.561 for allylic ring protons, indicating that a mixture of isomers is present.

Analysis.Calcd. for C H N (percent): C, 87.4; H, 7.3; N, 5.3. Found (percent): C, 87.8; H, 7.6; N, 5.3.

The isomer indicated by the triplet, 3-(4-dimethylaminonaphthyl)-1,3,5-cycloheptatriene, is isolated by stirring 2.6 g. (0.010 mole) of the mixture in 50 ml. of ethanol for 5 min. with 3 ml. of 40% aqueous tertafluoroboric acid, removing the solvent, and recrystallizing the solid from ethanol, M.P. 197199 C. The amine is liberated with aqueous sodium bicarbonate and extracted into ether to give 0.6 g. of product. The ultraviolet spectrum of this isomer has A max. 323 mu (log E 4.03).

EXAMPLE 12 Organic photoconductors of the type described herein 0 are separately incorporated into a coating dope having the following composition:

Organic photoconductor0.15 g.

Polymeric binder--0.50 g.

Sensitizer0.002 g.

Methylene chloride or tetrahydrofuran5 ml.

These compositions are then separately coated at a wet thickness of 0.004 inch on an aluminum surface maintained at 100 F. to provide the coatings described in Tables 1, 2 and 3 below. In a darkened room, the surface of each of the photoconductive layers so prepared is charged negatively to a potential of about 600 volts under a corona charger. The charged layer is covered with at transparent sheet bearing a pattern of opaque and lighttransmitting areas and exposed to the radiation from a 60 watt incandescent lamp at a distance of 100 cm. which provides an illumination intensity of about meter candles. The resultant latent image is developed by cascading over the surface of the layer a mixture of positively charged thermoplastic toner particles and glass beads, and the print fixed by heating. A reproduction of the original pattern results. The polymeric binder used in the coating compositions is a polyester of terephthalic acid and a mixture of ethylene glycol (1 part by weight)v and 2,2-bis(4-hydroxyethoxyphenyl)propane (9 parts by Weight). The sensitizers referred to in the tables are as follows:

(A) no sensitizer added;

(B) 2, 6-bis (4-ethylphenyl) -4- (4-amyloxyphenyl) -thiapyrylium perchlorate;

(C) 2,4,7-trinitrofluorenone;

(D) Crystal violet;

(E) Rhodamine B.

The coating of di 5 (5H dibenzo[a,d]cycloheptenyl) ether, incorporating B as the sensitizer referred to in Table 1, when tested as described above, produces an image with an expsoure time of 1.1 sec. and is assigned a relative speed of 100. In comparison to this, the other coatings when tested give relative speeds as shown in Table. 1.

TABLE 1 Sensi- Relative Photoconduetor tizcr speed Di-[5-(5H-dibenzo[a, d]cycloheptenyl)]-ether B 5-hydroxy-5H-dibenz0[a,d]cycloheptene B 83 1-[5-(5H-dibenzo[a, d]cycloheptenyl)]-4, 5-tli-carb0- B 67 methoxy-l, 2, 3-triazole. 1-[5-(5H-dibenzo[a, d]cycloheptenyl)]-4, ddi-benzoyk B 42 1, 2, 3-triazole. 5-azido-5H-dibenzo[a, d]cycloheptene B 21 EXAMPLE 13 The procedure of Example 12 is repeated except that each of the photoconductive layers is initially charged positively and the latent image developed with a negatively charged toner. Relative speeds are determined in the same manner.

EXAMPLE 14 The procedure of Example 12 is repeated except that the relative speeds of the photoconductive layers are determined for both negative and positive charging. The results are set forth in Table 3.

A photoconductive element is prepared in the manner set forth in Example 12 except that the photoconductor used is 3-(4-dimethylaminopheny1)-1,3,5-cycloheptatriene. After dark adapting, the sample is charged under a positive corona and then exposed through a step tablet (0.15 density increments) for 12 seconds at a distance of 13 inches from a BOO-watt incandescent lamp. The exposed strips are then toned by conventional cascade development with a negatively charged thermoplastic toner. The toner image is fixed at 300-3S0 for one minute forming a-permanent image. The number of steps developed by this procedure is a measure of the photosensitivity of the system. Sixteen steps are developed using the above photoconductor. This procedure is repeated with various photoconductors. The number of steps developed is set forth in Table 4.

TABLE 4 S ensi- Steps Photoconductor tlzer developed 3-(4-dimethylaminophenyl)-l,3,5-cyeloheptatriene B 16 3-r4- dimethylaminonaphthyl) -l,3,5-eyclhepta- B 19 trlene. 3-(4-diethylamino-2-methylphenyl)-1,3,&cyolo- B 22 heutatriene. Triphenylamine B 2124 The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinbefore and as defined in the appended claims.

I claim:

1. An electrophotographic element comprising an electrically conducting support having coated thereon a photoconductive composition comprising a polymeric filmforming binder and a photoconducting amount of a photoconductor having a structure selected from the group consisting of:

wherein 10 (C) (R1 and R2), (R3 and R4), (R5 and R6) and (R7 and R are together the necessary atoms to complete a benzene ring fused to the cyoloheptenyl nucleus.

2. An electrophotographic element as defined by claim 1 wherein the photoconductive composition is sensitized with a sensitizer selected from the group consisting of a pyrylium salt, a thiapyrylium salt, a selenapyrylium salt, a fluorene, a carboxylic acid and a triphenyl methane dye.

3. An electrophotographic element comprising an electrically conducting support having coated thereon a phoconductive composition comprising a polymeric binder and a photoconducting amount of a photoconductor selected from the group consisting of (4-dimethylaminophenyl) -1, 3 ,5 -cycloheptatriene,

(4-diethylamino-2-methylphenyl) -1, 3 ,5 -cycloheptatriene,

(4-dimethylaminonaphthyl)-1,3,5-cycloheptatriene,

di- [5 SH-dibenzo a,d] cycloheptenyl) ether,

5 -hydroxy-5H-dibenzo [a,d] cycloheptene,

1-[5-(5H-dibenzo[a,d1cycloheptenyl) -4,5-dicarbomethoxy-1,2, 3 -triazole,

1- [5- SH-dibenzo [a,d] cycloheptenyl) ]-4,5-dibenzoyl- 1,2,3-triazole,

5 -azido-5 H-dibenzo [a,d] cycloheptene,

4- [S-(SH-dibenzo [a,d] cycloheptenyl) ]-N,N-dimethyl aniline,

N,N-diethyl-3-methyl-4- [5- SH-dibenzo [a,d] cycloheptenyl) aniline,

4- 5- (SH-dibenzo [a,d] cycloheptenyl) aniline,

4- 5- (SH-dibenzo [a,d] cycloheptenyl) -1-dimethy1- aminonaphthalene,

1- 5-( 10,1l-dihydro-SH-dibenzo[a,d]cycloheptenyl)]- 4,5 -dibenzoyl-1,2,3-triazole,

1- [5-( 10,11-dihydro-5H-dibenzo [a,d]cycloheptenyl) 4,5-dicarbomethoxy-1,2,3-triazo1e, and

N,N-diethy1-3 -methyl-4- [5-( 10,1 l-dihydro-SH-dibenzo- [a,d] cycloheptenyl) aniline.

4. An electrophotographic element as defined in claim I 3 wherein the photoconductive composition is sensitized with a sensitizer selected from the group consisting of a pyrylium salt, a thiapyrylium salt, a selenapyrylium salt, a fluorene, a carboxylic acid and a triphenyl methane dye.

5. A photoconductive element for use in electrophotography comprising an electrically conducting support having coated thereon a photoconductive composition comprising:

(a) about 10 to by Weight based on said photoconductive composition of 4-[5-(5H-dibenzo[a,d] cycloheptenyl)] N,N dimethyl aniline as a photoconductor,

(b) a film-forming polymeric binder for the said photoconductor, and

(c) a sensitizer for the said photoconductor.

6. A photoconductive element for use in electrophotography comprising an electrically conducting support having coated thereon, a photoconductive composition comprising:

(a) about 10 to 60% by weight based on said photoconductive composition of N,N-diethyl-3-methyl-4- [5 (5H dibenzo[a,d]cycloheptenyl)]aniline as a photoconductor,

(b) a film-forming polymeric binder for the said photoconductor, and

(c) a sensitizer for the said photoconductor.

7. A photoconductive element for use in electrophotography comprising an electrically conducting support having coated thereon a photoconductive composition comprising:

(a) about 10 to 60% by weight based on said photoconductive composition of 4-[5-(5H-dibenzo[a,d] cycloheptenyl)] 1 dimethylaminonaphthalene as a photoconductor,

(b) a film-forming polymeric binder for the said photoconductor, and

(c) a sensitizer for the said photoeonductor.

8. A photoconductive element for use in electrophotography comprising an electrically conducting support having coated thereon a photoconductive composition comprising:

(a) about 10 to 60% by weight based on said photoconductive composition of N,N-diethyl-3-methyl-4- [5 (10,11 dihydro 5H dibenzo[a,d]cycloheptenyl)]aniline as a photoconductor,

(b) a film-forming polymeric binder for the said photoconductor, and

(c) a sensitizer for the said photoconductor.

9. A photoconductive element for use in electrophotography comprising an electrically conducting support having coated thereon a photoconductive composition comprising:

(a) about 10 to 60% by Weight based on said photoconductive composition of 3 (4 diethylamino 2- methylphenyl) 1,3,5 cycloheptatriene as a photoconductor,

(b) a film-forming polymeric binder for the said pho toconductor, and

(c) a sensitizer for the said photoconductor.

References Cited UNITED STATES PATENTS 7/1964 Davis et al. 96-1 5/1966 Van Allen et a1. 961

OTHER REFERENCES Jutz and Voithenleitner article in Chemische Benitite vol. 97, pp. 30 and 45, 1964.

Chemical Abstracts 6th Collective Index 1957-61, Subject Index, pp. 3542, 3543, 3815, 3816.

GEORGE F. LESMES, Primary Examiner I. C. COOPER III, Assistant Examiner U.S. Cl. X.R. 

